72,032 research outputs found
On the Complexity of Rule Discovery from Distributed Data
This paper analyses the complexity of rule selection for supervised learning in distributed scenarios. The selection of rules is usually guided by a utility measure such as predictive accuracy or weighted relative accuracy. Other examples are support and confidence, known from association rule mining. A common strategy to tackle rule selection from distributed data is to evaluate rules locally on each dataset. While this works well for homogeneously distributed data, this work proves limitations of this strategy if distributions are allowed to deviate. To identify those subsets for which local and global distributions deviate may be regarded as an interesting learning task of its own, explicitly taking the locality of data into account. This task can be shown to be basically as complex as discovering the globally best rules from local data. Based on the theoretical results some guidelines for algorithm design are derived. --
Distributed archive and single access system for accelerometric event data : a NERIES initiative
We developed a common access facility to homogeneously formatted
accelerometric event data and to the corresponding sheet of ground motion
parameters. This paper is focused on the description of the technical
development of the accelerometric data server and the link with the
accelerometric data explorer. The server is the third node of the 3-tier
architecture of the distributed archive system for accelerometric data. The
server is the link between the data users and the accelero- metric data portal.
The server follows three main steps: (1) Reading and analysis of the end-user
request; (2) Processing and converting data; and (3) Archiving and updating the
accelerometric data explorer. This paper presents the description of the data
server and the data explorer for accessing data
OGC SWE-based Data Acquisition System Development for EGIM on EMSODEV EU Project
The EMSODEV[1] (European Multidisciplinary
Seafloor and water column Observatory DEVelopment) is an EU
project whose general objective is to set up the full
implementation and operation of the EMSO distributed Research
Infrastructure (RI), through the development, testing and
deployment of an EMSO Generic Instrument Module (EGIM).
This research infrastructure will provide accurate records on
marine environmental changes from distributed local nodes
around Europe. These observations are critical to respond
accurately to the social and scientific challenges such as climate
change, changes in marine ecosystems, and marine hazards. In
this paper we present the design and development of the EGIM
data acquisition system. EGIM is able to operate on any EMSO
node, mooring line, sea bed station, cabled or non-cabled and
surface buoy. In fact a central function of EGIM within the
EMSO infrastructure is to have a number of ocean locations
where the same set of core variables are measured
homogeneously: using the same hardware, same sensor
references, same qualification methods, same calibration
methods, same data format and access, and same maintenance
procedures.Peer ReviewedPostprint (published version
Adaptive Dynamics of Realistic Small-World Networks
Continuing in the steps of Jon Kleinberg's and others celebrated work on
decentralized search in small-world networks, we conduct an experimental
analysis of a dynamic algorithm that produces small-world networks. We find
that the algorithm adapts robustly to a wide variety of situations in realistic
geographic networks with synthetic test data and with real world data, even
when vertices are uneven and non-homogeneously distributed.
We investigate the same algorithm in the case where some vertices are more
popular destinations for searches than others, for example obeying power-laws.
We find that the algorithm adapts and adjusts the networks according to the
distributions, leading to improved performance. The ability of the dynamic
process to adapt and create small worlds in such diverse settings suggests a
possible mechanism by which such networks appear in nature
Real-time growth rate for general stochastic SIR epidemics on unclustered networks
Networks have become an important tool for infectious disease epidemiology.
Most previous theoretical studies of transmission network models have either
considered simple Markovian dynamics at the individual level, or have focused
on the invasion threshold and final outcome of the epidemic. Here, we provide a
general theory for early real-time behaviour of epidemics on large
configuration model networks (i.e. static and locally unclustered), in
particular focusing on the computation of the Malthusian parameter that
describes the early exponential epidemic growth. Analytical, numerical and
Monte-Carlo methods under a wide variety of Markovian and non-Markovian
assumptions about the infectivity profile are presented. Numerous examples
provide explicit quantification of the impact of the network structure on the
temporal dynamics of the spread of infection and provide a benchmark for
validating results of large scale simulations.Comment: 45 pages, 8 figures, submitted to Mathematical Biosciences on
29/11/2014; Version 2: resubmitted on 15/04/2015; accepted on 17/04/2015.
Changes: better explanations in introduction; restructured section 3.3 (3.3.3
added); section 6.3.1 added; more precise terminology; typos correcte
Chandra X-ray observation of the HII region Gum 31 in the Carina Nebula complex
(abridged) We used the Chandra observatory to perform a deep (70 ksec) X-ray
observation of the Gum 31 region and detected 679 X-ray point sources. This
extends and complements the X-ray survey of the central Carina nebula regions
performed in the Chandra Carina Complex Project. Using deep near-infrared
images from our recent VISTA survey of the Carina nebula complex, our Spitzer
point-source catalog, and optical archive data, we identify counterparts for
75% of these X-ray sources. Their spatial distribution shows two major
concentrations, the central cluster NGC 3324 and a partly embedded cluster in
the southern rim of the HII region, but majority of X-ray sources constitute a
rather homogeneously distributed population of young stars. Our color-magnitude
diagram analysis suggests ages of ~1-2 Myr for the two clusters, whereas the
distributed population shows a wider age range up to ~10 Myr. We also identify
previously unknown companions to two of the three O-type members of NGC 3324
and detect diffuse X-ray emission in the region. Our results suggests that the
observed region contains about 4000 young stars in total. The distributed
population is probably part of the widely distributed population of ~ 1-10 Myr
old stars, that was identified in the CCCP area. This implies that the global
stellar configuration of the Carina nebula complex is a very extended stellar
association, in which the (optically prominent) clusters contain only a
minority of the stellar population.Comment: Accepted for publication in Astronomy & Astrophysics. A high quality
preprint is available at
http://www.usm.uni-muenchen.de/people/preibisch/publications.htm
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